The present invention is an improvement of the Coolant Recovery System, of which I am a joint inventor, described and claimed in application, U.S. Ser. No. 254,751 filed Apr. 16, 1981, now U.S. Pat. No. 4,366,069. The earlier coolant recovery system, while also recovering a heavier coolant fluid from a contaminated mixture, uses multiple-pass fluid flow of the fluid and the contaminated mixture through the system because of limited settling area and retention time. It is designed to accommodate, in comparison to the present invention, relatively high volumes of fluid at its optimum performance.
In the industries in which the coolant recovery system and the present invention are directed, a certain degree of cost-effectiveness and flexibility in the systems are required. The earlier coolant recovery system was one solution to the industries' needs. The present invention provides yet another answer to industry demands for a system to recover valuable fluids which would otherwise be disposed of after only one use. It is believed the present invention is an advancement in the state of the art for fluid recovery systems. A single-pass of the contaminated mixture through the system effectively recovers the heavier or coolant fluid. A minimum of equipment is required to achieve significant recovery results efficiently and with less expense. For example, the present invention utilizes a more dependable means of skimming, namely fluid displacement, to remove surface carried lighter fluid. In contrast, other systems might use various mechanical skimmers, or, as in the earlier coolant recovery system, a forced vortex might be used to skim the contaminated fluid tank surface. It is believed the skimming means of the present invention provides a more dependable means than those requiring mechanical devices to effect the skimming.
Whereas the earlier coolant recovery system required a preset amount of contaminated coolant to be introduced into the system for cleaning, the present invention is believed able to accommodate any amount up to 150 gallons per batch. Furthermore, the earlier coolant recovery system utilized the oil concentrate tank exclusively for collecting oil from the centrifuge. In contrast, the present invention utilizes an oil concentrate tank to collect surface oil from the contaminated fluid volume, in addition to capturing oil from the centrifuge.
In the earlier invention the centrifuge is the primary means of separation which, during service and maintenance of the centrifuge, makes the system vulnerable to downtime. In the present invention the centrifuge is used to "polish" the fluid and remove mechanically emulsified oils, with the dragout assembly removing all particles larger than 15 (based upon steel sp. gr. 7.0 gm/cc). For most machine tool operations this level of clarity is more than adequate. Thus if the centrifuge requires maintenance and is thus inoperative, the system will provide adequate filtration without interruption.
Also in the earlier coolant recovery system, the idle mode or off-cycle recirculating mode is not capable of recirculating the complete volume of coolant in the clean tank. Only twenty percent of the coolant may be recirculated. The present invention may provide recirculation of one hundred percent of the clean coolant in the storage tank during the fifth step of the present invention.
Additionally, in the earlier coolant recovery system, fines and oil globules are able to build up in the bottom of the clean tank thus requiring occasional maintenance by plant personnel. In the present invention, fines which may conceivably collect in the bottom of the clean tank are picked up by the transfer pump during the second or oil skimming step, thus discouraging the build up of fines and other contaminants in the bottom of the clean tank.
Furthermore, in the earlier system, the clean tank was designed to overflow into a semi-clean tank which accepted the skimmed surface oil. The centrifuge would then have to be activated to remove the skimmed oil. Certain mechanical emulsification was likely to occur in the feed pump during the transfer of the skimmed oil to the centrifuge, thus making the filtration process rather inefficient. The present invention "isolates" floating oil, preventing it from going into the centrifuge, by utilizing direct overflow skimming of the clean tank, and introducing any floating oil thus skimmed into the dragout assembly, where it will eventually be transferred into the oil concentrator tank.